Measurement system

ABSTRACT

A measurement system according to one aspect of the present invention includes a battery pack and at least one type of connected device to which the pack is connected. The pack includes a first detection device detecting a predetermined physical quantity in the pack and having a predetermined measurement range. The connected device includes a second detection device detecting a physical quantity the same as the predetermined physical quantity and having a measurement range different from the range of the first detection device. One of the pack and the connected device includes a receiving device and a measurement processing device that performs a predetermined measurement process by using one of: a detection-value-related information received by the receiving device; and a detection result by one device of the first detection device and the second detection device, the one device being provided in one of the pack and the connected device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation of application Ser. No. 13/939,485 filed Jul. 11,2013, which claims the benefit of Japanese Patent Application No.2012-156592 filed on Jul. 12, 2012 in the Japan Patent Office. Thedisclosure of the prior applications is hereby incorporated by referenceherein in its entirety.

BACKGROUND

The present invention relates to a measurement system that measures aphysical quantity in a battery pack.

There has been a known battery pack that contains a rechargeable batteryand includes a function of calculating a remaining battery capacity ofthe rechargeable battery. The remaining battery capacity calculated bythe battery pack can be used for various purposes; for example, in anelectric power tool to which this battery pack is attached and which isoperated by electric power from the rechargeable battery, the calculatedremaining battery capacity is used to display the remaining batterycapacity of the rechargeable battery in a simplified manner.

There have been known various methods of calculating a remaining batterycapacity of a rechargeable battery. For example, Unexamined JapanesePatent Application Publication No. 2010-164322 discloses the followingtechnique: a value of a discharge current is detected by an electriccurrent detection unit provided inside assembled cells; the detectedvalue is successively integrated so as to calculate a value of adischarge capacity; the value of the discharge capacity is deducted froma value of a capacity in a fully-charged state, thereby calculating avalue of the remaining battery capacity.

Moreover, Japanese Patent No. 3225119 discloses the following technique:in a battery pack, an electric-current detection resistor that detects avalue of a charge current and a value of a discharge current from arechargeable battery is provided; both of a time-integrated value of thedetected value of the charge current and a time-integrated value of thedetected value of the discharge current are added or deducted, therebycalculating a value of the remaining battery capacity. By taking intoaccount both of the discharge and charge in the above-described manner,the remaining battery capacity can be more accurately calculated.

SUMMARY

However, in a battery pack for an electric power tool, there may be acase where a value of a charge current is, for example, around 10 A at amaximum, while a value of a discharge current exceeds, for example, 100A at a maximum, and therefore, the value of the charge current isgreatly different from the value of the discharge current. For thisreason, if it is intended to detect both of the value of the chargecurrent and the value of the discharge current by the same singleelectric-current detection unit provided inside the battery pack, thiselectric-current detection unit essentially needs to be configured to becapable of measuring an electric current value up to around 100 A.Therefore, as the electric current value becomes lower, an error of thedetection becomes greater. Consequently, it is difficult to accuratelycalculate the remaining battery capacity.

Even when focusing only on the discharge current, the value of thedischarge current may be high, for example, exceed 100 A, or may be low,for example, 10 A or below, and dependent on an operation state of theelectric power tool. Thus, a fluctuation range of the value of thedischarge current is greater. Therefore, as the value of the dischargecurrent during operation is lower, an accuracy of the detection becomeslow, causing a greater detection error. As a result, it becomesdifficult to accurately calculate the remaining battery capacity.

The aforementioned problem in calculating the remaining battery capacityin the battery pack is one example, and the same problem as theaforementioned problem may occur when other detection objects (physicalquantities) are detected by a detection device. Specifically, it isnecessary to configure such that, as a range of a physical quantity as adetection object is greater, the detection device is capable ofdetecting a value up to a maximum value within the range. Thus, thelower a detection value is, the lower the detection accuracy becomes.

As above, in one aspect of the present invention, it is preferable thata physical quantity can be detected with high accuracy by using a simpleconfiguration, regardless of a range of the physical quantity as adetection object.

One aspect of the present invention is a measurement system providedwith a battery pack containing a battery, and at least one type ofconnected device to which the battery pack is to be connected. Thebattery pack includes a first detection device that is configured todetect a predetermined physical quantity in the battery pack and thathas a predetermined measurement range. The at least one type ofconnected device includes a second detection device that is configuredto detect a physical quantity and that has a measurement range differentfrom the measurement range of the first detection device, the physicalquantity being the same as the predetermined physical quantity. One ofthe battery pack and the at least one type of connected device is afirst device, and the other of the battery pack and the at least onetype of connected device is a second device. The first device includes areceiving device and a measurement processing device. The receivingdevice is configured to receive a detection-value-related informationthat is transmitted from the second device and that directly orindirectly indicates a detection result by one of the first detectiondevice and the second detection device. The measurement processingdevice is configured to perform a predetermined measurement process byusing one of: the detection-value-related information received by thereceiving device; and a detection result by one device of the firstdetection device and the second detection device, the one device beingprovided in the first device. The second device includes a transmissiondevice configured to transmit the detection-value-related information tothe first device. Here, the measurement range means a maximum value of aphysical quantity in a measurement range (detection range) that can benormally detected by the first detection device and the second detectiondevice.

In the above-constituted measurement system of the present invention,the battery pack and the at least one type of connected device areprovided with the respective detection devices for detection of the samephysical quantity. Although these detection devices detect the samephysical quantity as a detection object, the detection devices havedifferent respective measurement ranges from each other. Therefore, ifthe physical quantity is great, this physical quantity can be accuratelydetected by the detection device having the higher measurement range. Onthe other hand, if the physical quantity is small, this physicalquantity can be accurately detected by the detection device having thelower measurement range.

Moreover, to the measurement processing device, the detection result bythe detection device in the first device provided with this measurementprocessing device is transmitted. In addition, the detection result(detection-value-related information) by the detection device in thesecond device is transmitted to the measurement processing device fromthe second device. Thereby, the measurement processing device can easilyobtain both of the detection results by the detection devices having thedifferent measurement ranges.

Thus, the measurement system of the present invention makes it possibleto highly-accurately detect a physical quantity as a detection object bya simple configuration, regardless of a range of the physical quantity.

The first detection device and the second detection device may detectany physical quantity as a detection object. For example, the firstdetection device and the second detection device may be configured todetect an electric current to be discharged from the battery or to becharged to the battery, as the physical quantity.

In this case, the electric current is detected by the differentmeasurement ranges, respectively, of the first detection device and thesecond detection device. Accordingly, by performing the measurementprocess with the detection result of each of the detection devices, itis possible to perform the measurement process with high accuracy.

If the physical quantity as the detection object is an electric current,the first detection device may be configured to detect a value of theelectric current in a predetermined first measurement range, and thesecond detection device may be configured to detect a value of theelectric current in a predetermined second measurement range lower thanthe first measurement range.

In the measurement system configured as above, in a case of an electriccurrent having a relatively large value, the detection result by thefirst detection device is adopted, while in a case of an electriccurrent having a relatively small value, the detection result by thesecond detection device is adopted. Thereby, even if a variation rangeof the electric current is great, the measurement processing device canobtain an electric current value (or information indicating the electriccurrent value) with high accuracy to perform the measurement process.

In the above-constituted measurement system, various devices can beconsidered as the at least one type of connected device. For example, abattery charger that charges the battery may be provided as the at leastone type of connected device. In this system in which the battery packand the battery charger are connected to each other, the measurementprocessing device may be configured to perform, during discharging ofthe battery, the measurement process by using a detection result by thefirst detection device, and during charging of the battery by thebattery charger, the measurement process by using a detection result bythe second detection device.

That is to say, comparing a discharge current when the battery pack isconnected to another connected device and an electric power of thebattery is consumed by the another connected device, with a chargecurrent when the battery is charged by the battery charger, in general,the discharge current is usually, relatively greater than the chargecurrent, although it depends on a consumed electric power of the anotherconnected device.

In view of the above, during discharge of the battery, the detectionresult by the first detection device provided in the battery pack isused, while during charge of the battery from the battery charger, thedetection result by the second detection device provided in the batterycharger is used. Thereby, even if there is a greater difference betweenthe discharge current and the charge current, the measurement processingdevice can obtain an electric current value (or information indicatingthe electric current value) with high accuracy to perform themeasurement process.

Moreover, in the system in which the battery pack and the batterycharger are connected to each other in the above-described manner, thebattery pack may include the receiving device and the measurementprocessing device. The battery charger may include the transmissiondevice. The measurement processing device may be configured to perform,as the measurement process, calculation of a remaining battery capacityof the battery.

In the above-constituted measurement system, the measurement processingdevice provided in the battery pack obtains information indicating acharge current at a time of charge, from the battery charger. Therefore,even if a value of the charge current is small, it is possible to obtainhighly accurate information of the charge current detected in thebattery charger. For this reason, when calculating a remaining batterycapacity of the battery, the remaining battery capacity during chargecan be calculated with high accuracy, thereby improving accuracy of thecalculation as a whole of the remaining battery capacity.

As the at least one type of connected device, for example, an electricdevice to be operated by an electric power of the battery may beprovided. In the system in which the battery pack and the batterycharger are connected to each other in the above-described manner, thebattery pack may include the receiving device and the measurementprocessing device. The electric device may include the transmissiondevice. The measurement processing device may be configured such that,when the detection-value-related information is received from theelectric device, the measurement processing device performs themeasurement process by using the detection-value-related informationreceived from the electric device, and when the detection-value-relatedinformation is not received from the electric device, the measurementprocessing device performs the measurement process by using a detectionresult of the first detection device.

As explained above, the measurement processing device provided in thebattery pack generally uses the detection result by the detection deviceprovided in the battery pack (the first detection device), and alsouses, if the detection-value-related information is received from theelectric device, the received detection-value-related information. Withthis configuration, it is also possible to obtain the discharge currentduring discharge to the electric device, with high accuracy.

Such a configuration is especially effective in a case where the valueof the discharge current is a small value with respect to themeasurement range provided in the battery pack, such as when a ratedpower of the electric device is small or when the electric device isoperated under light load. Moreover, in such a case, if the measurementprocessing device is configured to perform, as the measurement process,calculation of a remaining battery capacity of the battery, it ispossible to obtain even the discharge current having a small value withhigh accuracy so as to reflect the obtained discharge current in thecalculation of the remaining battery capacity. Therefore, an improvedaccuracy of the calculation of the remaining battery capacity can beachieved.

Furthermore, if the physical quantity as a detection object is anelectric current, the transmission device may transmit informationdirectly indicating the detected electric current value. However, thetransmission device may transmit, for example, a result oftime-integration of (integrating) the electric current value, asinformation indirectly indicating the electric current value.

That is to say, the second device may include an electric-currentintegration device configured to calculate an electric-currentintegration value by performing a time-integration of a value of anelectric current detected by one of the first detection device and thesecond detection device, the one being provided in the second device. Inthis case, the transmission device is configured to transmit theelectric-current integration value calculated by the electric-currentintegration device, as the detection-value-related information.

As explained above, the measurement system is configured to perform, asthe measurement process, a process using the electric-currentintegration value, not by transmitting the detection result, as it is,of an electric current, but by transmitting the detection result as theelectric-current integration value. In this case, a calculation load inthe measurement process can be reduced. Moreover, if theelectric-current integration value in the second device is intended tobe calculated in the first device, it is necessary to obtain theelectric current value from the second device in a relatively shortcycle (i.e., receive the electric current value that has beentransmitted from the second device) and perform time-integration of theobtained electric current value. This causes a very frequentcommunication between the battery pack and the connected device.

In this regard, if the electric-current integration value is transmittedto a receiving-side device, the receiving-side device does not need toperform time-integration of the electric current value. Thus, thefrequency of the communication can be reduced.

Moreover, the above-described calculation of the remaining batterycapacity can be performed based on a result of a time integration of theelectric current value. Therefore, if it is configured such thatcalculation of the remaining battery capacity is performed as themeasurement process, the electric-current integration value istransmitted as the detection-value-related information; thisconfiguration is more effective in terms of both load in the measurementprocess and load in the communication.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described below, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a configuration diagram showing a schematic configuration of abattery pack and a battery charger of the present embodiment;

FIG. 2 is a configuration diagram showing a schematic configuration ofthe battery pack and an electric power tool of the present embodiment;

FIG. 3 is a flowchart showing a remaining-battery-capacity calculationprocess executed by a battery controller of the battery pack;

FIG. 4 is a flowchart showing a charge-capacity transmission processexecuted by a charge controller of the battery charger;

FIG. 5 is a flowchart showing a discharge-capacity transmission processexecuted by a motor controller of the electric power tool;

FIG. 6 is a flowchart showing a battery-voltage transmitting processexecuted by the battery controller of the battery pack; and

FIG. 7 is a flowchart showing a battery-voltage obtaining processexecuted by the charge controller of the battery charger.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present embodiment is an embodiment in which the present inventionis applied to calculation of a remaining battery capacity of a batteryin a battery pack of an electric power tool.

As shown in FIG. 1, a battery pack 1 contains a battery (rechargeablebattery) 11. When being connected to a battery charger 3, the batterypack 1 is configured to be able to charge the battery 11 from thebattery charger 3. FIG. 1 shows a state where the battery pack 1 isattached to the battery charger 3 thereby to electrically connect thebattery pack 1 and the battery charger 3 to each other.

As shown in FIG. 2, the battery pack 1 is configured to be attachable toand detachable from an electric power tool 5. When being attached to theelectric power tool 5, the battery pack 1 can operate the electric powertool 5 by supplying an electric power of the battery 11 to the electricpower tool 5. FIG. 2 shows a state where the battery pack 1 is attachedto the electric power tool 5 thereby to electrically connect the batterypack 1 and the electric power tool 5 to each other.

Hereinafter, specific configurations of the battery pack 1, the batterycharger 3, and the electric power tool 5 will be described withreference to FIGS. 1 and 2.

The battery pack 1 is attachable to and detachable from the electricpower tool 5 (see FIG. 2) as well as other various electric equipments(not shown), and is used as a power source for the electric power tool 5and the various electric devices.

The battery pack 1 is, as shown in FIGS. 1 and 2, provided with thebattery 11, a monitoring IC 12, a battery controller 13, a battery-sidecurrent detection circuit 14, a positive electrode terminal 21, anegative electrode terminal 22, a first signal terminal 23, and a secondsignal terminal 24.

The battery 11 is constituted of a plurality of (four in the presentembodiment) battery cells 16 to 19 connected in series. Each of thebattery cells 16 to 19 of the present embodiment is a lithium-ionrechargeable battery that generates a direct current (DC) voltage of 3.6V on a standalone basis. Accordingly, the battery 11 as a wholegenerates a DC voltage of 14.4 V. The configuration of the battery 11shown in FIG. 1 is merely one example, and a number, a connection state,a voltage, etc., of battery cells constituting the battery 11 should notbe limited to the configuration in FIG. 1.

A positive electrode of the battery 11 (i.e., positive electrode of thebattery cell 16 on a highest potential side) is connected to thepositive electrode terminal 21. A negative electrode of the battery 11(i.e., negative electrode of the battery cell 19 on a lowest potentialside) is connected to the negative electrode terminal 22 via thebattery-side current detection circuit 14.

The monitoring IC 12 is an integrated circuit (IC) for monitoring thebattery 11. The monitoring IC 12 has functions, such as a function ofdetecting a voltage of the battery 11 to output the detected voltage tothe battery controller 13, and a function of monitoring a voltage ofeach of the battery cells 16 to 19 of the battery 11 and, when at leastone of the voltages of the battery cells 16 to 19 is in an overvoltagestate, outputting to the battery controller 13 a signal (overvoltagesignal) indicating generation of the overvoltage.

The battery-side current detection circuit 14 is provided in a currentpath extending from the negative electrode terminal 22 to the negativeelectrode of the battery 11. The battery-side current detection circuit14 detects a value of an electric current flowing through this currentpath, i.e., a value of a charge current to be charged to the battery 11and a value of a discharge current discharged from the battery 11.

The battery-side current detection circuit 14 of the present embodimentincludes a shunt resistor provided in the current path extending fromthe negative electrode terminal 22 to the negative electrode of thebattery 11. The battery-side current detection circuit 14 is configuredto output a voltage between both ends of the shunt resistor, as a signalindicating a value of an electric current flowing through the shuntresistor, to the battery controller 13.

Used as the shunt resistor of the battery-side current detection circuit14 is a resistor that has a resistance value relatively smaller than aresistance value of a shunt resistor of a battery-charger-side currentdetection circuit 34, which will be described later, and a resistancevalue of a shunt resistor of a power-tool-side current detection circuit54 (see FIG. 2), which will be described later. Accordingly, ameasurement range of the battery-side current detection circuit 14 isrelatively higher than measurement ranges of the battery-charger-sidecurrent detection circuit 34 and the power-tool-side current detectioncircuit 54.

More specifically, in the present embodiment, the battery-side currentdetection circuit 14 of the battery pack 1 has a higher measurementrange of about 100 A and is capable of detecting an electric current ofup to 100 A. The reason why the battery-side current detection circuit14 has the higher measurement range as described above is that, amongvarious electric power tools to which the battery pack 1 can beattached, there exists a high-load (high output) electric power toolthat operates by receiving a supply of an electric current of around 100A at a maximum. In order to allow detection of such a large electriccurrent, the measurement range of the battery-side current detectioncircuit 14 is set to be high.

On the other hand, the battery-charger-side current detection circuit 34of the battery charger 3 and the power-tool-side current detectioncircuit 54 of the electric power tool 5 have the respective measurementranges that are low and about 10 A. The reason why thebattery-charger-side current detection circuit 34 has the lowmeasurement range as described above is that a value of a charge currentused to charge the battery pack 1 from the battery charger 3 is around10 A at most.

Although detailed explanations will be given later, the battery pack 1is configured to calculate a value of a remaining battery capacity ofthe battery 11, based on a value of the discharge current from thebattery 11 and a value of the charge current to the battery 11.Therefore, the battery pack 1 is configured to calculate a value of adischarge capacity during discharge by using a detection result by thebattery-side current detection circuit 14 provided in the battery pack1. Moreover, the battery pack 1 is configured to calculate a value of acharge capacity during charge by using a detection result by thebattery-charger-side current detection circuit 34 provided in thebattery charger 3.

It is also possible to detect a charge current during charge by thebattery-side current detection circuit 14 of the battery pack 1.Therefore, the battery pack 1 can also calculate a value of the chargecapacity during charge by using the detection result by the battery-sidecurrent detection circuit 14 provided in the battery pack 1.

However, as described above, the measurement range of the battery-sidecurrent detection circuit 14 is high and about 100 A. Thus, if a lowelectric current of about 10 A is detected by the detection circuithaving such a high measurement range, it would be difficult to obtain ahighly accurate detection result. Consequently, it is difficult tocalculate the value of the charge capacity with high accuracy, resultingin difficulty of calculating the value of the remaining battery capacityof the battery 11 with high accuracy.

In view of the above, in the present embodiment, thebattery-charger-side current detection circuit 34 having the lowmeasurement range is provided in the battery charger 3 so that the valueof the charge current during charge can be detected with high accuracyin the battery-charger-side current detection circuit 34. The batterypack 1 is configured to obtain a detection result by thebattery-charger-side current detection circuit 34 during charge(specifically, by obtaining a time-integrated value of the detectionresults) to calculate the value of the charge capacity.

Moreover, compared with various electric power tools to which thebattery pack 1 can be attached, the electric power tool 5 (see FIG. 2)of the present embodiment has a smaller rated current. In this electricpower tool 5, a value of an electric current supplied from the batterypack 1 during operation is about 10 A at most, which is substantiallythe same as the value of the charge current. Thus, in a case where thebattery pack 1 is attached to the electric power tool 5 to operate theelectric power tool 5, if a smaller discharge current to the electricpower tool 5 is detected by the battery-side current detection circuit14 of the battery pack 1, the same problem as that described withrespect to the charge current (i.e., deterioration of detectionaccuracy) arises.

In view of the above, in the present embodiment, the power-tool-sidecurrent detection circuit 54 having the lower measurement range isprovided in the electric power tool 5 having a smaller rated power, sothat a value of a discharge current to the electric power tool 5 isdetected with high accuracy by this power-tool-side current detectioncircuit 54. Moreover, it is configured such that the battery pack 1obtains a detection result by the power-tool-side current detectioncircuit 54 during discharge to the electric power tool 5 (specifically,obtain a time-integrated value of the detection results) to calculatethe value of the charge capacity. Here, specific numerical values ofeach of the aforementioned electric currents and each of the measurementranges are merely one example.

The battery controller 13 has various functions including a function ofobtaining a voltage of the battery 11 from the monitoring IC 12 tomonitor a battery voltage, a function of performing a predeterminedprotection operation when the overvoltage signal has been inputted fromthe monitoring IC 12, and a remaining-battery-capacity calculationfunction that calculates a value of the remaining battery capacity ofthe battery 11.

In the present embodiment, the battery controller 13 is constituted of amicrocomputer. However, the battery controller 13 may be constituted invarious forms, for example, may be constituted of an IC (control IC)formed of various logic circuits, etc. A charge controller 33 and amotor controller 53, both of which will be described later, may beconstituted in various forms in the same manner as in the batterycontroller 13.

The battery controller 13 is connected to the first signal terminal 23and is configured to be capable of performing data communication withthe battery charger 3 and the electric power tool 5 via the first signalterminal 23. That is to say, when the battery pack 1 is attached to thebattery charger 3, the first signal terminal 23 of the battery pack 1 isconnected to a first signal terminal 43 of the battery charger 3,thereby allowing data communication with the charge controller 33 of thebattery charger 3. As a result, the battery controller 13 can obtain avalue of the charge capacity from the charge controller 33.

The battery controller 13 is also connected to the second signalterminal 24. It is configured such that, through this second signalterminal 24, a battery-charger connection signal CHG (voltage: Vdd) canbe inputted to the battery controller 13 from the battery charger 3.That is, when the battery pack 1 is attached to the battery charger 3,the second signal terminal 24 of the battery pack 1 is connected to asecond signal terminal 44 of the battery charger 3. Thus, when a controlvoltage Vdd is generated in the battery charger 3, the control voltageVdd is inputted as the battery-charger connection signal CHG to thebattery controller 13. The battery controller 13 can detect whether ornot connection to the battery charger 3 is established based on whetheror not the battery-charger connection signal CHG has been inputted.

Although the remaining-battery-capacity calculation function provided inthe battery controller 13 will be described later in detail withreference to FIGS. 3 to 5, a brief overview thereof is as follows. Thebattery controller 13 performs time-integration of (i.e., integrates)the value of the electric current detected by and inputted from thebattery-side current detection circuit 14, thereby calculating an amountof change in a capacity of the battery 11.

In the present embodiment, it is configured such that, while chargingfrom the battery charger 3 is performed, the value of the chargecapacity is inputted to the battery controller from the battery charger3 by data communication. Therefore, with respect to a capacity of acharge to be charged to the battery 11 during charge, the batterycontroller 13 obtains the value of the charge capacity, which isreceived from the battery charger 3, and uses the obtained value tocalculate a value of the remaining battery capacity.

Accordingly, basically, during discharge, the battery controller 13performs time-integration of the value of the electric current(discharge current) detected by the battery-side current detectioncircuit 14, thereby calculating a value of the discharge capacity; onthe other hand, during charge, the battery controller 13 obtains thevalue of the charge capacity transmitted from the battery charger 3.This value of the charge capacity is a value calculated by the chargecontroller 33 based on a value of the electric current (a charge currentvalue) detected by the battery-charger-side current detection circuit34. Then, the battery controller 13 calculates a value of the remainingbattery capacity of the battery 11, for example, by deducting the valueof the discharge capacity from or adding the value of the chargecapacity to a value of the charge capacity (a fully-charged capacityvalue) of the battery 11 in a fully-charged state.

However, since the electric power tool 5 shown in FIG. 2 has a smallrated power, the electric power tool 5 is configured to calculate avalue of the discharge capacity by the electric power tool 5 itself andtransmit the calculated value of the discharge capacity to the batterypack 1. Therefore, when the battery pack 1 is connected to the electricpower tool 5 and supplies an electric power to the electric power tool5, the battery pack 1 obtains the value of the discharge capacitytransmitted from the electric power tool 5 to calculate a value of theremaining battery capacity.

The battery pack 1 is further provided with a power supply circuit,which is not shown. The power supply circuit is configured to lower avoltage of the battery 11 to generate a control voltage having apredetermined voltage value. The monitoring IC 12 and the batterycontroller 13 are operated by this control voltage.

Next, the battery charger 3 will be described. The battery charger 3 is,as shown in FIG. 1, provided with an input rectifier circuit 31, acharging switching power supply circuit 32, the charge controller 33,the battery-charger-side current detection circuit 34, a voltagedetection circuit 35, a control power generation circuit 36, a positiveelectrode terminal 41, a negative electrode terminal 42, the firstsignal terminal 43, and the second signal terminal 44.

The input rectifier circuit 31 rectifies an alternate voltage suppliedfrom an alternating current (AC) power source such as a commercial powersource. Such a rectified output is outputted to the charging switchingpower supply circuit 32 and the control power generation circuit 36.

The charging switching power supply circuit 32 is a switching powersupply circuit that generates a direct-current charging power to becharged to the battery 11 based on an output from the input rectifiercircuit 31. The charging switching power supply circuit 32 isdrive-controlled by the charge controller 33.

The battery-charger-side current detection circuit 34 is provided in acurrent path extending from the negative electrode terminal 42 to anegative terminal among positive and negative output terminals (notshown) of the charging switching power supply circuit 32. Thebattery-charger-side current detection circuit 34 detects a value of anelectric current flowing through this current path, i.e., a value of acharge current to be charged to the battery 11.

The battery-charger-side current detection circuit 34 of the presentembodiment includes a shunt resistor provided in the current pathextending from the negative electrode terminal 42 to the negativeterminal of the charging switching power supply circuit 32. Thebattery-charger-side current detection circuit 34 is configured tooutput a voltage between both ends of the shunt resistor, as a signalindicating a value of an electric current flowing through the shuntresistor, to the charge controller 33.

The value of the charge current used to charge the battery by thebattery charger 3 of the present embodiment is, as described above,around 10 A at most. Thus, the shunt resistor of thebattery-charger-side current detection circuit 34 has a resistance valuerelatively greater than the resistance value of the shunt resistor ofthe battery-side current detection circuit 14 in the battery pack 1.That is to say, the measurement range of the battery-charger-sidecurrent detection circuit 34 is relatively lower than the measurementrange of the battery-side current detection circuit 14 and is, forexample, about 10 A in the present embodiment.

The voltage detection circuit 35 detects a value of the voltage (batteryvoltage) of the battery 11 in the battery pack 1 and inputs a signalindicating the value of the detected battery voltage to the chargecontroller 33.

The control power generation circuit 36 is a switching power supplycircuit that generates a predetermined control voltage Vdd (for example,DC 3.3 V) based on an output from the input rectifier circuit 31. Thecontrol voltage Vdd generated by the control power generation circuit 36is used as a power source for operating the charge controller 33; inaddition, when the battery pack 1 is attached to the battery charger 3,the control voltage Vdd generated by the control power generationcircuit 36 is outputted from the second signal terminal 44 to thebattery pack 1, as the battery-charger connection signal CHG.

In the present embodiment, the charge controller 33 is constituted of amicrocomputer as in the battery controller 13 inside the battery pack 1.The charge controller 33 drive-controls the charging switching powersupply circuit 32, based on various information received from thebattery controller 13 in the battery pack 1 by data communication orbased on the value of the battery voltage detected by the voltagedetection circuit 35, thereby controlling a charge pattern (chargecurrent, charge voltage, etc.) to the battery 11.

Moreover, the charge controller 33 performs time-integration of (i.e.,integrates) the value of the electric current (charge current) detectedby the battery-charger-side current detection circuit 34 for eachpredetermined period of time, thereby calculating a value of the chargecapacity that has been charged to the battery 11 for the predeterminedperiod of time. The charge controller 33 then transmits the calculatedvalue of the charge capacity from the first signal terminal 43 to thebattery pack 1.

Next, the electric power tool 5 will be described. The electric powertool 5 includes, as shown in FIG. 2, a motor 51, a drive switchingelement 52, the motor controller 53, the power-tool-side currentdetection circuit 54, a trigger switch 55, a positive electrode terminal61, a negative electrode terminal 62, and a signal terminal 63.

The positive electrode terminal 61 is connected to one end of the motor51 via the trigger switch 55. The negative electrode terminal 62 isconnected to the other end of the motor 51 via the power-tool-sidecurrent detection circuit 54 and the drive switching element 52.

The motor 51 of the present embodiment is a brushed direct current (DC)motor. Moreover, the motor 51 of the present embodiment has a smallrated power, and a value of an electric current during operation of themotor 51 is around 10 A at most. Among various electric power tools thatare used with the battery pack 1 attached thereto, some of the electricpower tools have a large rated power and a value of an electric currentduring operation thereof reaches around 100 A at a maximum. Comparingwith the some of the electric power tools, the electric power tool 5 ofthe present embodiment is considered to be an electric power tool havinga smaller rated power.

The trigger switch 55 is turned on and off when a user operates atrigger, which is not shown, provided in the electric power tool 5.Specifically, the trigger switch 55 is turned on when the user pulls thetrigger, while the trigger switch 55 is turned off when the userreleases the trigger. Information on on-and-off states of the triggerswitch 55 is inputted to the motor controller 53.

When the trigger switch 55 is turned on, the motor controller 53 turnson the drive switching element 52 to start conduction of electriccurrent from the battery pack 1 to the motor 51, thereby operating themotor 51. When the trigger switch 55 is turned off, the motor controller53 turns off the drive switching element 52 to interrupt the conductionof electric current to the motor 51. Here, the drive switching element52 is an N-channel MOSFET in the present embodiment; however, this ismerely one example.

The power-tool-side current detection circuit 54 is provided in acurrent path extending from the negative electrode terminal 62 to thedrive switching element 52. The power-tool-side current detectioncircuit 54 detects a value of an electric current flowing through thiscurrent path, i.e., a value of a discharge current discharged from thebattery 11 to the motor 51.

The power-tool-side current detection circuit 54 of the presentembodiment includes a shunt resistor provided in the current pathextending from the negative electrode terminal 62 to the drive switchingelement 52. The power-tool-side current detection circuit 54 isconfigured to output a voltage between both ends of the shunt resistor,as a signal indicating a value of an electric current flowing throughthe shunt resistor, to the motor controller 53.

The value of the discharge current when the electric power tool 5 in thepresent embodiment is operated is, as described above, around 10 A atmost. Thus, the shunt resistor of the power-tool-side current detectioncircuit 54 has a resistance value relatively greater than the resistancevalue of the shunt resistor of the battery-side current detectioncircuit 14 in the battery pack 1. That is to say, the measurement rangeof the power-tool-side current detection circuit 54 is relatively lowerthan the measurement range of the battery-side current detection circuit14 and is, for example, about 10 A in the present embodiment.

The motor controller 53 performs time-integration of (i.e., integrates)the value of the electric current (discharge current) detected by thepower-tool-side current detection circuit 54 for each predeterminedperiod of time, thereby calculating a value of the discharge capacitythat has been discharged from the battery 11 for the predeterminedperiod of time. Then, the motor controller 53 transmits the calculatedvalue of the discharge capacity from the signal terminal 63 to thebattery pack 1.

Next, the remaining-battery-capacity calculation function provided inthe battery controller 13 of the battery pack 1 will be described inmore detail with reference to flowcharts in FIGS. 3 to 5.

FIG. 3 shows a remaining-battery-capacity calculation process that isexecuted by the battery controller 13 to calculate a value of theremaining battery capacity of the battery 11. Before describing thisremaining-battery-capacity calculation process, a charge-capacitytransmission process to be executed in the battery charger 3 and adischarge-capacity transmission process to be executed in the electricpower tool 5 will be described.

First, explanations will be given with respect to the charge-capacitytransmission process executed by the charge controller 33 in the batterycharger 3, with reference to FIG. 4.

In a memory (not shown) provided in the charge controller 33, a programfor the charge-capacity transmission process in FIG. 4 is stored. When aCPU (not shown) provided in the charge controller 33 starts operating byreceiving a supply of the control voltage Vdd, the CPU executes thecharge-capacity transmission process in FIG. 4.

When the charge-capacity transmission process in FIG. 4 is started,first in S210, the charge controller 33 determines whether or notcharging of the battery 11 is being performed. Since the chargecontroller 33 has a basic function of controlling charging to thebattery 11, understandably, the charge controller 33 itself candetermine whether or not charging is being performed.

While charging is not performed (S210: NO), this determination processof S210 is repeatedly performed. On the other hand, if charging is beingperformed (S210: YES), in S220, a charge-current value Ic is detected.Specifically, a detection result of an electric current is obtained fromthe battery-charger-side current detection circuit 34. Based on thisdetection result, the charge-current value Ic is detected.

Then, in S230, a charge-capacity value Cc is calculated. During charge,this process of S230 is performed each time a predetermined timeinterval Δt has elapsed. The charge-capacity value Cc is calculated inS230 by the following formula (1).

Cc=Cc+Ic·Δt  (1)

That is, each time the time interval Δt has elapsed, the charge-capacityvalue Cc calculated at the current time interval Δt is added in acumulative manner (i.e., time-integrated) to the charge-capacity valueCc calculated at the previous time interval Δt.

Then, in S240, it is determined whether or not a transmission timing hasbeen reached. The transmission timing is a timing that is reached in apredetermined cycle, which is at least greater than the aforementionedΔt (for example, tens to several hundreds of times of Δt).

If the transmission timing has not been reached (S240: NO), it isdetermined in S250 whether or not charging is being performed. Whencharging is being performed, the process returns to S220. In otherwords, while charging is performed, the calculations in S220 and S230are repeated until the transmission timing has been reached, therebytime-integrating the charge-capacity value Cc.

If the transmission timing has been reached (S240: YES) or if chargingis stopped although the transmission timing has not yet been reached(S250: NO), in S260, the charge-capacity value Cc that is currentlycalculated is transmitted to the battery pack 1. In S270, the currentlycalculated charge-capacity value Cc is set to “0” and thereafter, theprocess returns to S210.

Next, the discharge-capacity transmission process executed by the motorcontroller 53 of the electric power tool 5 will be described withreference to FIG. 5.

In a memory (not shown) provided in the motor controller 53, a programfor the discharge-capacity transmission process in FIG. 5 is stored.When a CPU (not shown) provided in the motor controller 53 startsoperating, the CPU executes the discharge-capacity transmission processin FIG. 5.

When the discharge-capacity transmission process in FIG. 5 is started,first in S310, the motor controller 53 determines whether or notdischarging is being performed, i.e., whether or not discharging fromthe battery pack 1 to the motor 51 is being performed. Thisdetermination can be performed, for example, based on a detection resultby the power-tool-side current detection circuit 54 or based on whetheror not the trigger switch 55 is turned on.

While discharging is not performed (S310: NO), this determinationprocess in S310 is repeatedly performed. On the other hand, ifdischarging is being performed (S310: YES), in S320, a discharge-currentvalue Idx is detected. Specifically, a detection result of an electriccurrent is obtained from the power-tool-side current detection circuit54. Based on the detection result, the discharge-current value Idx isdetected.

Then, in S330, a discharge-capacity value Cdx is calculated. Duringdischarge, this process of S330 is performed each time a predeterminedtime interval Δt has elapsed. The discharge-capacity value Cdx iscalculated in S330 by the following formula (2).

Cdx=Cdx+Idx·Δt  (2)

That is, in the same manner as in the process of S230 in FIG. 4 in thebattery charger 3, each time the time interval Δt has elapsed, thedischarge-capacity value Cdx calculated at the current time interval Δtis added in a cumulative manner (i.e., time-integrated) to thedischarge-capacity value Cdx calculated at the previous time intervalΔt.

Then, in S340, it is determined whether or not a transmission timing hasbeen reached. In the same manner as in the process of S240 in FIG. 4 inthe battery charger 3, the transmission timing is a timing that isreached in a predetermined cycle, which is at least greater than theaforementioned Δt (for example, tens to several hundreds of times ofΔt).

If the transmission timing has not been reached (S340: NO), it isdetermined in S350 whether or not discharging is being performed. Whendischarging is being performed, the process returns to S320. In otherwords, while discharging is performed, the calculations in S320 and S330are repeated until the transmission timing has been reached, therebytime-integrating the discharge-capacity value Cdx.

If the transmission timing has been reached (S340: YES) or ifdischarging is stopped although the transmission timing has not yet beenreached (S350: NO), in S360, the discharge-capacity value Cdx that iscurrently calculated is transmitted to the battery pack 1. In S370, thecurrently calculated discharge-capacity value Cdx is set to “0” andthereafter, the process returns to S310.

Next, the remaining-battery-capacity calculation process executed by thebattery controller 13 in the battery pack 1 will be described withreference to FIG. 3.

In a memory (not shown) provided in the battery controller 13, a programfor the remaining-battery-capacity calculation process in FIG. 3 isstored. When a CPU (not shown) provided in the battery controller 13starts operating, the CPU executes the remaining-battery-capacitycalculation process in FIG. 3.

When the remaining-battery-capacity calculation process in FIG. 3 isstarted, first in S110, the battery controller 13 determines whether ornot discharging is being performed, i.e., whether or not discharging isbeing performed from the battery 11. This determination can beperformed, for example, based on a detection result by the battery-sidecurrent detection circuit 14, contents of communication between thebattery controller 13 and other external microcomputers, or presence orabsence of the battery-charger connection signal CHG from the batterycharger 3.

While discharging is not performed (S110: NO), it is determined in S180whether or not charging is being performed, i.e., whether or notcharging of the battery 11 is being performed by the battery charger 3.This determination can be performed in the same manner as in S110.

If charging is not being performed (S180: NO), the process returns toS110. If charging is being performed (S180: YES), it is determined inS190 whether or not calculated data of the charge-capacity value Cc hasbeen received from the battery charger 3. If the calculated data of thecharge-capacity value Cc has not been received (S190: NO), the processreturns to S110. If the calculated data of the charge-capacity value Cchas been transmitted from the battery charger 3 and this transmittedcalculated data has been received (S190: YES), in S200, a remainingbattery capacity value C of the battery 11 is calculated. Specifically,the remaining battery capacity value C is calculated by the followingformula (3).

C=C+Cc  (3)

That is, by adding the newly received charge-capacity value Cc to thecurrent remaining battery capacity value C, the remaining batterycapacity value C is updated. Here, an initial value of the remainingbattery capacity value C may be set, for example, such that a remainingbattery capacity at a time of manufacturing of the battery pack 1 ismeasured and such a measured value is set as an initial value of theremaining battery capacity value C. Alternatively, each time the battery11 is charged by the battery charger 3 to reach a predetermined capacity(e.g., a fully charged state), a value of the capacity at such a timemay be set as an initial value of the remaining battery capacity valueC. After the remaining battery capacity value C is calculated in S200,the process returns to S110.

On the other hand, if it is determined in S110 that discharging is beingperformed (S110: YES), it is determined in S120 whether or notcalculated data (Cdx) of a discharge-capacity value Cd is beingcommunicated.

The electric power tool 5 of the present embodiment has a function inwhich the electric power tool 5 itself calculates a discharge-capacityvalue Cdx and transmits the calculated discharge-capacity value Cdx tothe battery pack 1. Therefore, when the battery pack 1 is attached tothe electric power tool 5, a predetermined communication process isexecuted between the battery controller 13 and the motor controller 53.Then, the battery controller 13 makes a preparation for receiving thedischarge-capacity value Cdx from the electric power tool 5, while themotor controller 53 of the electric power tool 5 makes a preparation fortransmitting the calculated data of the discharge-capacity value Cdx.

As described above, when the battery controller 13 makes the preparationfor receiving the discharge-capacity value Cdx from an external deviceby communicating with a device to be connected, the battery controller13 determines in S120 that the communication is being performed (S120:YES) (i.e., the discharge-capacity value Cdx is to be supplied from theexternal device). Then, the process proceeds to S160.

In S160, it is determined whether or not the calculated data of thedischarge-capacity value Cdx has been received from the external device(e.g., the electric power tool 5, etc.). If the calculated data of thedischarge-capacity value Cdx is not received (S160: NO), the processreturns to S110. If, for example, when the battery pack 1 is attached tothe electric power tool 5, the calculated data of the discharge-capacityvalue Cdx has been transmitted from the electric power tool 5 and thenreceived (S160: YES), in S170, a remaining battery capacity value C ofthe battery 11 is calculated. Specifically, the remaining batterycapacity value C is calculated by the following formula (4).

C=C−Cdx  (4)

That is, by deducting the newly received discharge-capacity value Cdxfrom the current remaining battery capacity value C, the remainingbattery capacity value C is updated. After the remaining batterycapacity value C is calculated in S170, the process returns to S110.

On the other hand, if it is determined in S120 that the communication ofthe calculated data Cdx of the discharge-capacity value Cd is not beingperformed (S120: NO), the process proceeds to S130 to calculate thedischarge-capacity value Cd by the battery controller 13 itself. InS130, a discharge-current value Ido is detected. Specifically, adetection result of an electric current is obtained from thebattery-side current detection circuit 14. Based on the detectionresult, the discharge-current value Ido is detected.

Then, in S140, a discharge-capacity value Cdo is calculated. Duringdischarge, this process of S140 is performed each time a predeterminedtime interval Δt has elapsed. The discharge-capacity value Cdo iscalculated in S140 by the following formula (5).

Cdo=Ido·Δt  (5)

Then, in S150, the calculated discharge-capacity value Cdo is used tocalculate a remaining battery capacity value C. Specifically, theremaining battery capacity value C is calculated by the followingformula (6).

C=C−Cdo  (6)

That is, by deducting the calculated discharge-capacity value Cdobetween the previous time interval Δt and the current time interval Δt,from the current remaining battery capacity value C, the remainingbattery capacity value C is updated. After the remaining batterycapacity value C is calculated in S150, the process returns to S110.

As described above, the battery pack 1 of the present embodimentperforms calculation of the remaining battery capacity value C basicallyas follows: during discharge, the battery controller 13 calculates theremaining battery capacity value C by using the discharge-capacity valueCdo detected and calculated by the battery controller 13 itself, andduring charge, the battery controller 13 calculates the remainingbattery capacity value C by using the charge-capacity value Cc receivedfrom the battery charger 3.

However, as in the electric power tool 5 of the present embodiment shownin FIG. 2, if the battery controller 13 is connected to an equipment,etc. configured to detect and calculate the discharge-capacity value Cdxso as to transmit such a discharge-capacity value Cdx to the batterypack 1, the battery controller 13 calculates the remaining batterycapacity value C by using the discharge-capacity value Cdx received fromthe equipment, etc.

The measurement range of the battery-side current detection circuit 14in the battery pack 1 is set to have a relatively high value (about 100A in the present embodiment). This is because there may be a case wherea large electric current flows from the battery pack 1 depending on anelectric power tool to which the battery pack 1 is to be connected. Forthis reason, if a value of the electric current is small, such as thecharge current from the battery charger 3 and the discharge current tothe electric power tool 5, it is difficult to accurately detect such asmall value of the electric current.

In view of the above, in the battery charger 3 and the electric powertool 5, the respective current detection circuits having the lowermeasurement ranges (about 10 A in the present embodiment) are provided.The value of the charge current from the battery charger 3 is detectedby the battery-charger-side current detection circuit 34 that has thelow measurement range and that is provided in the battery charger 3.Based on this detected value of the charge current, the chargecontroller 33 calculates a value of the charge capacity.

Moreover, with respect to the discharge current to the electric powertool 5, the value of the discharge current is detected by thepower-tool-side current detection circuit 54 that has the lowmeasurement range and that is provided in the electric power tool 5.Based on this detected value of the discharge current, the motorcontroller 53 calculates a value of the discharge capacity.

As above, both of the value of the charge capacity calculated by thebattery charger 3 and the value of the discharge capacity calculated bythe electric power tool 5 are highly accurate.

In this way, with the simple configuration in which the respectivecurrent detection circuits having the lower measurement ranges areprovided in the battery charger 3 and the electric power tool 5 so as toobtain calculated results of respective values of the charge capacityand discharge capacity from the respective current detection circuits bydata communication, it can be achieved to calculate the remainingbattery capacity value C of the battery 11 with high accuracy by thebattery controller 13.

That is to say, even if the electric current flowing through the battery11 varies over a great range, it is possible to detect a value of suchan electric current with high accuracy. Moreover, based on the detectedvalue of the electric current, it is possible to calculate a value ofthe discharge capacity or a value of the charge capacity with highaccuracy. Consequently, the remaining battery capacity value C can becalculated with high accuracy.

Moreover, when the battery controller 13 calculates the remainingbattery capacity value C of the battery 11, it is not absolutelynecessary that a calculated result of the value of the charge capacityis transmitted to the battery controller 13 from the battery charger 3.It may be possible that data of the value of the charge current detectedin the battery charger 3 is transmitted to the battery controller 13 sothat the battery controller 13 can calculate a value of the chargecapacity by using the transmitted data.

Likewise, in the electric power tool 5, it is not absolutely necessarythat a calculated result of the value of the discharge capacity istransmitted to the battery controller 13 from the electric power tool 5.It may be possible that data of the value of the discharge currentdetected in the electric power tool 5 is transmitted to the batterycontroller 13 so that the battery controller 13 can calculate a value ofthe discharge capacity by using the transmitted data.

However, in the aforementioned configuration, the battery controller 13needs to repeatedly obtain electric current data in a short cycle toperform calculation (i.e., time-integration, etc.) of a value of thecapacity, causing a frequent data communication.

In this regard, in the present embodiment, transmitted from the batterycharger 3 is, not a value of the charge current, but a value of thecharge capacity calculated based on the value of the charge current.Moreover, transmitted from the electric power tool 5 is, not a value ofthe discharge current, but a value of the discharge capacity calculatedbased on the value of the discharge current. Therefore, in the presentembodiment, it is possible to reduce frequency of data communicationbetween the battery pack 1 and a connected device to which the batterypack 1 is connected.

Here, in the present embodiment, both the battery charger 3 and theelectric power tool 5 correspond to an example of a connected device ofthe present invention; specifically, the electric power tool 5corresponds to an example of an electric device of the presentinvention. The battery-side current detection circuit 14 corresponds toan example of a first detection device of the present invention. Boththe battery-charger-side current detection circuit 34 and thepower-tool-side current detection circuit 54 correspond to an example ofa second detection device of the present invention. The batterycontroller 13 corresponds to an example of a measurement processingdevice and an example of a receiving device of the present invention.Each of the charge controller 33 and the motor controller 53 correspondsto an example of a transmission device and an example of anelectric-current integration device of the present invention.

Each of the process in S230 in FIG. 4 and the process in S330 in FIG. 5corresponds to an example of a process executed by the electric currentintegration device of the present invention. The processes in S150,S170, and S220 in FIG. 3 correspond to an example of a process executedby the measurement processing device of the present invention.

MODIFICATION

The embodiment of the present invention has been described as above.However, embodiments of the present invention should not at all belimited to the above-described embodiment. Needless to say, the presentinvention can be carried out in various forms without departing from thetechnical scope of the present invention.

For example, a physical quantity as a detection object is not limited toan electric current and may be any object that can be detected by boththe battery pack 1 and a connected device to be connected to the batterypack 1. As a specific example, for instance, a value of the batteryvoltage may be transmitted from the battery pack 1 during charge.

When charging the battery 11, the charge controller 33 in the batterycharger 3 performs a charge control while concurrently monitoring avoltage of the battery 11. In order to appropriately perform the chargecontrol, the battery voltage needs to be detected with accuracy as highas possible. Since the battery charger 3 includes the voltage detectioncircuit 35 for detection of the battery voltage, it is, of course,possible to perform the charge control by using a detection result bythe voltage detection circuit 35. Meanwhile, since the battery pack 1 ofthe present embodiment includes the monitoring IC 12, it is possible todetect the battery voltage by the monitoring IC 12 in a relativelyhighly accurate manner. Therefore, by transmitting a battery-voltagevalue detected by the monitoring IC 12 to the battery charger 3 by datacommunication, the charge controller 33 can perform the charge controlwith much higher accuracy.

With reference to FIGS. 6 and 7, explanations will be given with respectto respective processes executed by the controllers 13 and 33 in a casewhere the battery voltage value is configured to be transmitted to thebattery charger 3 from the battery pack 1 in the above-described manner.

When a battery-voltage transmitting process in FIG. 6 is started, firstin S410, the battery controller 13 of the battery pack 1 determineswhether or not the battery 11 is being charged. If the battery 11 is notbeing charged, this battery-voltage transmitting process is terminated.However, if the battery 11 is being charged, it is determined in S420whether or not a battery-voltage transmission request has been receivedfrom the battery charger 3 by data communication.

If the battery-voltage transmission request has not been received fromthe battery charger 3, this battery-voltage transmitting process isterminated. However, if the battery-voltage transmission request hasbeen received, in S430, a battery-voltage value is detected.Specifically, a detected result of the battery-voltage value is obtainedfrom the monitoring IC 12. Then, in S440, the obtained battery-voltagevalue is transmitted to the battery charger 3.

When a battery-voltage obtaining process in FIG. 7 is started, first inS510, the charge controller 33 of the battery charger 3 transmits abattery-voltage transmission request to the battery pack 1 by datacommunication. Then, it is determined in S520 whether or not thebattery-voltage value has been received from the battery pack 1.

If it is determined that the battery-voltage value has not beenreceived, in S540, a battery-voltage value detected by the voltagedetection circuit 35 in the battery charger 3 is obtained as anon-provisional battery-voltage value for control. On the other hand, ifthe battery-voltage value has been received from the battery pack 1, inS530, the received battery-voltage value is obtained as anon-provisional battery-voltage value for control.

The above-described battery voltage is merely one example. The presentinvention can be applied to other various physical quantities.

Moreover, the value of the electric current discharged from the battery11 varies, depending on a connected device to which the battery pack 1is connected or an operational state (load state) of the connecteddevice. Therefore, transmission of a detection result (e.g., a dischargecapacity, etc.) from the connected device may not be performedconstantly as in the electric power tool 5 in the above-describedembodiment, but may be performed as needed depending on a variationrange of an electric current flowing through the connected device.

For example, it may be configured such that if a value of the dischargecurrent is large, the battery controller 13 calculates a value of aremaining battery capacity by using a detection result of thebattery-side current detection circuit 14 of the battery pack 1; on theother hand, if the value of the discharge current is small, the batterycontroller 13 sends a transmission request to the connected device (or,the connected device itself determines that the value of the dischargecurrent has become smaller), so that data of the value of the dischargecurrent or the value of the discharge capacity is transmitted to thebattery controller 13 from the connected device.

Moreover, in the present embodiment, the battery controller 13 isconfigured to calculate by itself a value of the remaining batterycapacity of the battery 11; however, it may be configured such that,depending on a physical quantity as a detection object, the connecteddevice to which the battery pack 1 is to be connected performs, by theconnected device itself, detection of the physical quantity or variouscalculation processes (measurement processes), etc., based on a resultof this detection.

Furthermore, an application of the present invention is not limited tothe configuration shown in FIG. 1 in which the battery pack 1 and thebattery charger 3 are provided, and the configuration shown in FIG. 2 inwhich the battery pack 1 and the electric power tool 5 are provided.Rather, the present invention can be applied to a configuration in whichthe battery pack 1 and any connected device that can be connected(attached) to the battery pack 1 are provided. Examples of the connecteddevice other than a battery charger are an electrical device, such as arechargeable radio, an electrical operating machine, such as arechargeable cleaner, and so on.

What is claimed is:
 1. A measurement system comprising: a battery packcontaining a battery; and at least one type of connected device to whichthe battery pack is to be connected, wherein the battery pack comprisesa first detection device that is configured to detect a predeterminedphysical quantity in the battery pack and that has a predeterminedmeasurement range, wherein the at least one type of connected devicecomprises a second detection device that is configured to detect aphysical quantity and that has a measurement range different from themeasurement range of the first detection device, wherein the physicalquantity is the same as the predetermined physical quantity, wherein oneof the battery pack and the at least one type of connected device is afirst device, and the other of the battery pack and the at least onetype of connected device is a second device, the first devicecomprising: a receiving device configured to receive adetection-value-related information that is transmitted from the seconddevice and that directly or indirectly indicates a detection result byone of the first detection device and the second detection device; and ameasurement processing device configured to (i) perform a predeterminedmeasurement process by using the detection-value-related informationreceived by the receiving device in a case where the receiving devicereceives the detection-value-related information and (ii) to ignore thedetection-value-related information failed to be received by thereceiving device not to thereby perform the measurement process in acase where the receiving device fails to receive thedetection-value-related information, the measurement process comprisingcalculation of a remaining battery capacity of the battery, and the onedevice being provided in the first device, and wherein the second devicecomprises a transmission device configured to transmit thedetection-value-related information to the first device.
 2. Themeasurement system according to claim 1, wherein the at least one typeof connected device comprises a battery charger that is configured tocharge the battery.
 3. A measurement system comprising: a battery packcontaining a battery; and a battery charger to which the battery pack isto be connected, wherein the battery pack comprises a first detectiondevice that is configured to detect a predetermined physical quantity inthe battery pack and that has a predetermined measurement range, whereinthe battery charger comprises: a second detection device that isconfigured to detect a physical quantity and that has a measurementrange different from the measurement range of the first detectiondevice, the physical quantity being the same as the predeterminedphysical quantity; and a transmission device configured to transmit adetection-value-related information to the first device, thedetection-value-related information directly or indirectly indicating adetection result by the second detection device, and wherein the batterypack comprises: a receiving device configured to receive thedetection-value-related information transmitted from the batterycharger; and a measurement processing device configured to (i) perform apredetermined measurement process by using the detection-value-relatedinformation received by the receiving device in a case where thereceiving device receives the detection-value-related information and(ii) to ignore the detection-value-related information failed to bereceived by the receiving device not to thereby perform the measurementprocess in a case where the receiving device fails to receive thedetection-value-related information, the measurement process comprisingcalculation of a remaining battery capacity of the battery.